Hydrogenation of formic acid to formaldehyde

ABSTRACT

An environmentally beneficial process for the production of fuels and chemicals employs carbon dioxide from a natural source or from an artificial chemical source that would otherwise be discharged into the environment. The carbon dioxide is converted to formic acid and the formic acid is then non-biologically converted to fuels and/or chemicals without the intermediate process of hydrogenating the formic acid to methanol or reacting the formic acid with ammonia to form formamide. In the present process, formic acid is converted to one of seven primary feedstocks: formaldehyde, acrylic acid, methane, ethylene, propylene, syngas, and C5-C7 carbohydrates. The formaldehyde, acrylic acid, methane, ethylene, propylene, syngas and/or short chain carbohydrates can either be used directly, or can be converted into a wealth of other products.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. Non-Provisional patent applicationSer. No. 12/830,338, filed on Jul. 4, 2010, and to correspondingInternational Application No. PCT/US2011/030098, filed on Mar. 25, 2011,both entitled “Novel Catalyst Mixtures”. The '338 non-provisional and'098 international applications both claimed priority benefits from U.S.Provisional Patent Application Ser. No. 61/317,955 filed on Mar. 26,2010, entitled “Novel Catalyst Mixtures”. This application is alsorelated to U.S. Non-Provisional patent application Ser. No. 13/626,873,filed on Sep. 25, 2012, which claimed priority benefits and continuationstatus from the '098 international application.

This application is also related to U.S. Non-Provisional patentapplication Ser. No. 13/174,365, filed Jun. 30, 2011, and toInternational Application No. PCT/US2011/042809, filed on Jul. 1, 2011,both entitled “Novel Catalyst Mixtures”. The '365 non-provisionalapplication claimed priority benefits from U.S. Provisional PatentApplication Ser. No. 61/484,072, filed on May 9, 2011, entitled “NovelCatalyst Mixtures”. The '809 international application claimed prioritybenefits from the '338 non-provisional, the '098 international, the '072provisional, and the '365 non-provisional applications.

The present application is also related to U.S. Non-Provisional patentapplication Ser. No. 13/530,058, filed on Jun. 21, 2012, entitled“Sensors For Carbon Dioxide And Other End Uses”, and correspondingInternational Patent Application No. PCT/US2012/043651, filed on Jun.22, 2012, entitled “Low Cost Carbon Dioxide Sensors”. The '058non-provisional and '651 international applications both claimedpriority benefits from U.S. Provisional Patent Application Ser. No.61/499,225, filed on Jun. 21, 2011, entitled “Low Cost Carbon DioxideSensors”.

This application is also related to U.S. Non-Provisional patentapplication Ser. No. 13/445,887, filed on Apr. 12, 2012,“Electrocatalysts For Carbon Dioxide Conversion”. The '887nonprovisional application claimed priority benefits from U.S.Provisional Application 61/499,225, filed on Jun. 21, 2011, entitled“Low Cost Carbon Dioxide Sensors”, and from U.S. Provisional PatentApplication Ser. No. 61/540,044, filed on Sep. 28, 2011, entitled “OnDemand Carbon Monoxide Generator for Therapeutic and OtherApplications”. The '887 non-provisional application also claimedpriority benefits and continuation-in-part status from the '338non-provisional application.

Each of the above applications is hereby incorporated by referenceherein in its entirety.

FIELD OF THE INVENTION

The present invention relates to catalytic chemistry and in particularto processes for catalytically converting carbon dioxide to useful fuelsor chemicals, including formaldehyde, acrylic acid, ethane, propane,ethylene, propylene, butene, and carbohydrates comprising at least 5carbon atoms.

BACKGROUND OF THE INVENTION

Recycling generated carbon dioxide back to fuels and chemicals wouldmake a tremendous difference to the U.S. economy. Presently, fuels andorganic chemicals are usually made from petroleum, coal, and/or naturalgas “fossil fuels.” However, if such fuels and chemicals could be madefrom CO₂, then the U.S. dependence on imported oil would be lessened,and emissions of greenhouse gases that are thought to contribute toglobal warming would be reduced. CO₂ produced in power plants wouldchange from a waste product to a useful, economically viable feedstock.Solar and wind energy could also be stored in the form of hydrocarbonfuels.

Presently, however, most large volume organic chemicals are made fromfossil fuels. For example, most acrylic acid produced in the U.S. iscurrently made from propylene. The propylene is made from petroleum.Most formaldehyde now produced in the U.S. is manufactured by oxidationof methanol. The methanol is manufactured from natural gas or coal.Ethylene is made by cracking of light olefins from petroleum, or frommethanol. If these products could be made from CO₂, the use of fossilfuels in the U.S. would be reduced, as would the emissions of greenhousegases.

U.S. Pat. No. 8,212,088 describes an environmentally beneficial processfor preparing a fuel or chemical, in which carbon dioxide from a naturalsource, or carbon dioxide from an artificial chemical source that wouldotherwise be discharged into the environment by the artificial chemicalsource, is converted to useful fuels and chemicals. In the processdescribed in the '088 patent, CO₂ is first converted to a mixture offormic acid and other compounds. The formic acid is then sent to asecond process where it undergoes a 4-electron hydrogenation to formmethanol. The methanol is then converted to fuels and chemicals usingconventional chemical processes, as illustrated in FIG. 1. The advantageof converting CO₂ to methanol is that infrastructure already exists toconvert methanol into other products.

The limitation in the process described in the '088 patent is that thehydrogenation to methanol is an extra step in the conversion processthat wastes energy, and that may not be needed at all. For example,almost half of the methanol produced worldwide is further reacted toyield formaldehyde via an oxidative dehydrogenation process. Energy iswasted when formic acid is first hydrogenated to methanol and thendehydrogenated to formaldehyde, as illustrated in FIG. 2A. Moreover, theintermediate methanol can be a safety hazard, because it is highlyflammable and the flame is invisible.

As described in more detail below, the present environmentallybeneficial process for the production of fuels and chemicals preferablyemploys carbon dioxide from a natural source or carbon dioxide from anartificial chemical source that would otherwise be discharged into theenvironment by the artificial chemical source. The carbon dioxide isconverted to formic acid and other products. The formic acid is thenconverted to fuels and/or chemicals without the intermediate process ofhydrogenating the formic acid to methanol or reacting the formic acidwith ammonia to form formamide.

By contrast, the '088 patent describes a method in which (a) carbondioxide is converted to formic acid and other products, (b) the formicacid is hydrogenated to form methanol, and then (c) the methanol isconverted to fuels and chemicals. For example, FIGS. 2A and 2B comparethe process for the formation of formaldehyde disclosed in the '088patent (FIG. 2A) and that disclosed in the present application (FIG.2B). As shown, the process disclosed in the present application useshalf as much hydrogen as the process described in the '088 patent, anddoes not require temperatures as high as those used in the processdescribed in the '088 patent.

In the process disclosed herein, only a small fraction (namely, lessthan 10%) of the formic acid is hydrogenated to methanol. In the presentprocess, formic acid can be made by any method, and the formic acid isthen converted to fuels and chemicals without the intermediate processof hydrogenating the formic acid to methanol or reacting it with ammoniato form formamide. The present process produces fuels and chemicals inwhich formic acid is converted to one of seven primary feedstocks:formaldehyde, acrylic acid, methane, ethylene, propylene, syngas, andC5-C7 carbohydrates, without the intermediate process of hydrogenatingthe formic acid to methanol or reacting it with ammonia to formformamide. The formaldehyde, acrylic acid, methane, ethylene, propylene,syngas and/or short chain carbohydrates can either be used directly, orcan be converted into a wealth of other products, as illustrated in FIG.3. The list of products in FIG. 3 is not meant to limit the presentprocess. Rather, it provides examples of products that can be made fromformic acid following the teachings of this application.

In the present process for the production of formaldehyde, and productsmade using formaldehyde, formic acid is converted to formaldehydewithout a separate intermediate process of hydrogenating the formic acidto methanol. The present process encompasses processes in which hydrogenreacts with formic acid to form formaldehyde. The process can occur inthe presence of a catalyst comprising an oxide of at least one of thefollowing elements: Mg, Ca, Sr, Ba, Ti, Y, Lu, Ti, Zr, Hf, V, Nb, Ta,Cr, Mo, W, Fe, Co, Ni, Cu, Zn, Al, Ga, In, Tl, Si, Ge, Sn, Sb, Bi, Se,Te, Pb, La, Ce, Pr, Th, Nd, Pm, U, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, orYb, preferably the oxides of cerium or tellurium. Reaction temperaturecan be between 8° C. and 350° C., preferably between 40° C. and 200° C.,most preferably between 60° C. and 100° C.

The present process also produces organic acids with at least threecarbon atoms specifically including acrylic acid, methyl acrylic acid orpropionic acid, wherein formic acid directly or indirectly reacts withan unsaturated hydrocarbon to yield the organic acid. The presentprocess encompasses systems for produce the organic acids from formicacid and an unsaturated hydrocarbon comprising at least two reactors inseries, in which the temperature of each reactor can be controlledindependently. The present process also encompasses systems with onereactor containing an acid catalyst and a second reactor containing acatalyst comprising at least one of a nickel salt, a copper salt and apalladium salt.

The present process also produces olefins such as ethylene and propyleneand products synthesized from olefins, in which formic acid is convertedto the olefins ethylene and/or propylene without a separate intermediateprocess of hydrogenating the formic acid to methanol. In the presentprocess, formic acid is first converted to formaldehyde as describedabove and the formaldehyde is then further converted to olefins such asethylene, propylene or butylene. The process can employ a base catalystto condense the formaldehyde into a multi-carbon species, followed by anacid catalyst to convert the multi-carbon species into olefins. The acidcatalyst can be in the form of a zeolite such as ZMS-5 or SAPO-43. Thepresent process encompasses the use of CO2 to modify the pH of themixture after some of the formaldehyde has been condensed. In someembodiments, the present process employs ZSM-5 or SAPO-43 in theconversion of formic acid to a product comprising propylene. ZSM-5 is analuminosilicate zeolite mineral belonging to the pentasil family ofzeolites, having the chemical formula is NanAlnSi96-nO192.16H2O(0<n<27); it is widely used in the petroleum industry as a heterogeneouscatalyst for hydrocarbon isomerization reactions (seehttp://en.wikipedia.org/wiki/ZSM-5, downloaded on Feb. 23, 2013).SAPO-43 is a small pore silico-alumino-phosphate (seehttp://pubs.acs.org/doi/abs/10.1021/1a026424j, downloaded on Feb. 23,2013).

The present process also produces carbohydrates or molecules producedfrom carbohydrates, in which formic acid is converted to a carbohydratewithout a separate intermediate process of hydrogenating the formic acidto methanol. In the present process, the formic acid is converted toformaldehyde as described above, and the formaldehyde is then reacted inthe presence of a base catalyst to yield a carbohydrate. Calciumhydroxide is a preferred catalyst in the present process, and thepresent process specifically encompasses the use of carbon dioxide forthe removal of calcium from solution.

The present process also produces syngas or molecules produced fromsyngas, in which formic acid is converted to syngas without a separateintermediate process of hydrogenating the formic acid to methanol. Thepresent process preferably employs two parallel reactors to convert theformic acid into syngas, wherein the temperatures of the two independentreactors can be independently controlled. It is preferred that one ofthe reactors contains an acid catalyst while the other reactorpreferably contains a metallic catalyst.

SUMMARY OF THE INVENTION

Shortcomings and limitations of existing processes for converting CO₂ touseful fuels or chemicals are overcome by a process for the productionof fuels and chemicals comprising the steps of forming an amount offormic acid and non-biologically converting the amount of formic acid toa product comprising an organic intermediate. Less than 10% of theamount of formic acid is hydrogenated to methanol or reacted withammonia to form formamide.

In a preferred embodiment, the process further comprises initiallyconverting an amount of carbon dioxide obtained from a natural source orfrom an artificial chemical source to produce the amount of formic acid,thereby reducing the amount of carbon dioxide present in nature ordiverting the amount of carbon dioxide from being discharged into theenvironment by the artificial chemical source.

The formic acid is preferably converted to a product comprising at leastone of formaldehyde, acrylic acid, ethane, propane, ethylene, propylene,butene, and a carbohydrate comprising at least five carbon atoms. In apreferred process, the formic acid is hydrogenated to form a productcomprising formaldehyde.

In a preferred embodiment, the process further comprises reacting theformic acid with hydrogen in the presence of a catalyst comprisingoxygen and at least one of Mg, Ca, Sr, Ba, Ti, Y, Lu, Ti, Zr, Hf, V, Nb,Ta, Cr, Mo, W, Fe, Co, Ni, Cu, Zn, Al, Ga, In, Tl, Si, Ge, Sn, Sb, Bi,Se, Te, Pb, La, Ce, Pr, Th, Nd, Pm, U, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,and Yb. The catalyst is preferably a metal oxide comprising at least oneof cerium (IV) oxide and tellurium (IV) oxide. In a preferred process,reaction temperature is between 8° C. and 300° C.

In a preferred embodiment, the process further comprises a formose stepin which the formaldehyde is converted to formose sugars. The formosestep preferably comprises reacting the formaldehyde in the presence ofCa(OH)₂ to produce C5 and C6 sugars. The process can further comprise ahydrocarbon step in which the formose sugars are converted to a productcomprising at least one of paraffin and olefins. The hydrocarbon steppreferably converts the formose sugars to a product comprising at leastone of ethane, propane, ethylene, propylene and butene. The hydrocarbonstep preferably employs a catalyst comprising a zeolite, more preferablya silico-alumino-phosphate zeolite or an aluminosilicate zeolite.

In a preferred embodiment, the process further comprises anacid-converting step in which the amount of formic acid is converted toan organic acid comprising at least 3 carbon atoms. The organic acid ispreferably at least one of acrylic acid and methylacrylic acid.

In a preferred embodiment, the process further comprises converting theformic acid to a product comprising at least one of carbon monoxide andhydrogen. The product comprising both of carbon monoxide and hydrogen ispreferably produced by reacting the formic acid in at least two parallelreactors having temperatures independently controllable. One of thereactors preferably contains a metallic catalyst capable of yieldinghydrogen. The other reactor preferably contains a catalyst comprising atleast one of an oxide, an acid and a base to yield carbon monoxide. Thehydrogen and carbon monoxide are mixed to yield syngas.

A process for the production of formaldehyde comprises hydrogenating anamount of formic acid to form a product comprising formaldehyde, inwhich the formaldehyde is formed without hydrogenating more than 10% ofthe amount of formic acid to methanol. The process preferably furthercomprises initially converting an amount of carbon dioxide obtained froma natural source or from an artificial chemical source to produce theamount of formic acid, thereby reducing the amount of carbon dioxidepresent in nature or diverting the amount of carbon dioxide from beingdischarged into the environment by the artificial chemical source.

In a preferred embodiment, the process for the production offormaldehyde further comprises reacting the formic acid with hydrogen inthe presence of a catalyst comprising oxygen and at least one of Mg, Ca,Sr, Ba, Ti, Y, Lu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Co, Ni, Cu, Zn,Al, Ga, In, Tl, Si, Ge, Sn, Sb, Bi, Se, Te, Pb, La, Ce, Pr, Th, Nd, Pm,U, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. The preferred catalyst is ametal oxide comprising at least one of cerium (IV) oxide and tellurium(IV) oxide. The preferred reaction temperature is between 8° C. and 350°C., more preferably between 40° C. and 200° C., and even more preferablybetween 60° C. and 100° C.

A process for the production of an organic acid having at least threecarbon atoms comprises the steps of forming an amount of formic acid andreacting the amount of formic acid with an amount of an unsaturatedhydrocarbon.

In a preferred embodiment of the process for the production of anorganic acid, the unsaturated hydrocarbon is preferably one of acetyleneand methylacetylene, and the organic acid is preferably one of acrylicacid and methyl acrylic acid. The reacting step is preferably performedin the presence of a mixture comprising a phosphine ligand, a strongacid and a catalyst comprising at least one of a palladium salt, acopper salt and a nickel salt. Reaction temperature is preferablybetween 50° C. and 350° C. The formic acid preferably contacts an acidcatalyst before being introduced into a vessel containing the mixture.The acid catalyst temperature is preferably different than the mixturetemperature, with the preferred acid catalyst temperature being at least100° C., more preferably at least 130° C.

A process for the production of at least one of a C5 sugar and a C6sugar comprises the steps of forming an amount of formic acid,non-biologically converting the amount of formic acid to a productcomprising an organic intermediate, in which less than 10% of the amountof formic acid is hydrogenated to form a product comprisingformaldehyde, and reacting the product comprising formaldehyde over abase catalyst to yield a solution comprising at least one of a C5 sugarand a C6 sugar.

In a preferred embodiment of the process for the production of at leastone of a C5 sugar and a C6 sugar, reaction temperature is between 50° C.and 70° C. The base catalyst preferably comprises Ca(OH)₂. The processpreferably further comprises removing calcium from the sugar solution bybubbling a gas comprising carbon dioxide through the sugar solution toproduce a sugar solution substantially free of calcium. The sugarsolution substantially free of calcium preferably has a pH value between4 and 7.

A process for the production of olefins comprises the steps of formingan amount of formic acid and non-biologically converting the amount offormic acid to a product comprising an organic intermediate in whichless than 10% of the amount of formic acid is hydrogenated to form aproduct comprising formaldehyde, reacting the product comprisingformaldehyde over a base catalyst comprising Ca(OH)₂ to yield a solutioncomprising at least one of a C5 sugar and a C6 sugar, removing calciumfrom the sugar solution by bubbling a gas comprising carbon dioxidethrough the sugar solution to produce a sugar solution substantiallyfree of calcium, and reacting the sugars in the presence of an acidcatalyst to form a product comprising at least one olefin. The preferredacid catalyst comprises a zeolite, more preferably asilico-alumino-phosphate zeolite.

A process for the production of propylene comprises the steps of formingan amount of formic acid; and non-biologically converting the amount offormic acid to a product comprising an organic intermediate, whereinless than 10% of the amount of formic acid is hydrogenated to form aproduct comprising formaldehyde, reacting the product comprisingformaldehyde over a base catalyst comprising Ca(OH)₂ to yield a solutioncomprising at least one of a C5 sugar and a C6 sugar, removing calciumfrom the sugar solution by bubbling a gas comprising carbon dioxidethrough the sugar solution to produce a sugar solution substantiallyfree of calcium, and reacting the sugars in the presence of analuminosilicate zeolite catalyst to form a product comprising propylene.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (Prior Art) is a schematic diagram of products that can beproduced from methanol, as described in the '088 patent.

FIG. 2 is a schematic diagram comparing (A) the process for formaldehydeproduction as described in the '088 patent to (B) the process forformaldehyde production as disclosed in the present application.

FIG. 3 is schematic diagram showing some of the products that can besynthesized from formic acid according to the teachings of the presentapplication. The dashed lines are examples from conventional, prior artprocesses. The solid lines are examples of processes described in thepresent application.

FIG. 4 is a schematic of the electrochemical cell employed in Example 1herein.

FIG. 5 is a gas chromatogram (GC) trace taken during CO₂ conversion toformic acid following the procedures in Example 1 herein.

FIG. 6 is a schematic diagram of the experimental apparatus for theconversion of formic acid to formaldehyde in Example 2 herein.

FIG. 7 is a mass spectrogram showing the m/z=30 ion (formaldehyde)observed during formic acid hydrogenation on a CeO₂ catalyst at 100° C.(plot 171) and 150° C. (plot 170).

FIG. 8 is a GC trace demonstrating the formation of ethylene (peak 401),propylene (peak 402) and butene (peak 403) in Example 4 herein. Otherproducts include dimethylether (peak 404), methane (peak 405), ethane(peak 406) and CO₂ (peak 407), as well as air (peak 408).

FIG. 9 is a GC trace demonstrating the formation of propylene (peak 410)in Example 5 herein. Other products include ethylene (peak 411), butene(peak 412), dimethylether (peak 413). Also seen in the trace are water(peak 414), CO₂ (peak 415) and air (peak 416).

FIG. 10 is a schematic diagram of the apparatus employed to convertformic acid and acetylene to acrylic acid in Example 6 herein.

FIG. 11 is a plot showing the growth of the acrylic acid GC peak duringthe experiments described in Example 6 herein.

FIG. 12 is a schematic diagram of the apparatus employed in Examples 7and 8 herein.

FIG. 13 are GC traces of the conversion of formic acid to CO on acatalyst available under the trade designation Dowex 50WX8, followingthe procedures described in Example 8 herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

The present process is not limited to the particular methodology,protocols, reagents described herein, as these can vary as personsfamiliar with the technology involved here will recognize. In addition,the terminology employed herein is for the purpose of describingparticular embodiments only, and is not intended to limit the scope ofthe present process.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include the plural reference unless the context dictatesotherwise. Thus, for example, a reference to “a linker” is a referenceto one or more linkers and equivalents thereof known to those familiarwith the technology involved here. Also, the term “and/or” is used toindicate one or both stated cases may occur, for example A and/or Bincludes (A and B) and (A or B).

Unless defined otherwise, the technical and scientific terms used hereinhave the same meanings as commonly understood by persons familiar withthe technology involved here. The features illustrated in the drawingsare not necessarily drawn to scale, and features of one embodiment canbe employed with other embodiments as persons familiar with thetechnology involved here would recognize, even if not explicitly statedherein.

Numerical value ranges recited herein include all values from the lowervalue to the upper value in increments of one unit, provided that thereis a separation of at least two units between a lower value and a highervalue. As an example, if it is stated that the concentration of acomponent or value of a process variable such as, for example, size,angle size, pressure, time and the like, is, for example, from 1 to 90,specifically from 20 to 80, more specifically from 30 to 70, it isintended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32, andso on, are expressly enumerated in this specification. For values lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1, asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value are to be treated in a similar manner.

Prior art references (patents and printed publications) referred toherein are incorporated by reference herein in their entirety.

Definitions

The term “Biological Reaction” refers to a chemical reaction that istaking place inside the cells of bacteria or yeast. “Biologicalreaction” also refers to reactions that use NADH or NADPH as a reactant.

The term “C5-C7 carbohydrates” refers to carbohydrates with 5 to 7carbon atoms.

The term “Certified ACS” refers to a chemical that is certified to meetthe specifications maintained by the American Chemical Society.

The term “EMIM” refers to the 1-ethyl-3-methylimidazolium cation.

The term “EMIM-BF4” refers to 1-ethyl-3-methylimidazoliumtetrafluoroborate.

The term “FAH” refers to formate dehydrogenase.

The term “FDH” refers to formaldehyde dehydrogenase.

The term “Formose Reaction” refers to the polymerization of formaldehydeto carbohydrates. The reaction includes carbohydrates formed by directcondensation of formaldehyde, namely, nH₂CO+H₂O→HO(CH₂O)_(n)H. Thereaction also includes carbohydrates formed by adding formaldehyde to asolution with a dilute concentration of carbohydrates in order to createadditional carbohydrates.

The term “Formose Sugars” refers to the carbohydrate products of theformose reaction.

The term “GC” refers to gas chromatography, a gas chromatographinstrument, or data from such an instrument represented as a gaschromatogram.

The term “ID” refers to inside diameter.

The term “NAD+” refers to nicotinamide adenine dinucleotide.

The term “NADH” refers to nicotinamide adenine dinucleotide, reduced.

The term “NADPH” refers to nicotinamide adenine dinucleotide phosphate,reduced.

The term “Non-Biological Reaction” refers to any chemical reaction otherthan a biological reaction.

The term “OD” refers to outside diameter.

The term “olefin” is an unsaturated chemical compound containing atleast one carbon-to-carbon double bond; also referred to as an alkene.

The term “Organic Intermediate” refers to a molecule other than CO thatcontains at least one carbon atom. This term typically does not includesalts containing the “inorganic” carbonate or bicarbonate anions, unlessthe compound also contains at least one additional carbon atom that isin an “organic” form, such as the carbon atoms in an acetate anion or atetramethyl ammonium cation.

The term “SAPO” refers to a silico-alumino-phosphate zeolite.

The term “TPD” refers to temperature programmed desorption.

The term “UHV” refers to ultra-high vacuum.

Specific Description

Formic acid offers several advantages as a starting material for theproduction of fuels and chemicals. Co-owned U.S. patent application Ser.No. 12/830,338 (the '338 application) describes the synthesis of formicacid at high efficiency via a two-electron reduction of carbon dioxide.The process is efficient and is less expensive than other processes forthe conversion of CO₂ into useful products.

The U.S. Food and Drug Administration lists formic acid as beinggenerally recognized as safe for human consumption. A solutioncontaining 85% formic acid in water is not spontaneously combustible, soit is safer to handle and transport than methanol.

Presently, however, formic acid is not used as a feedstock forindustrial chemicals. See, for example, Wikipedia(http://en.wikipedia.org/wiki/Formamide; downloaded on Nov. 8, 2012),reporting that formamide can be formed via a reaction of formic acid andammonia, but the process is no longer used industrially. Formic acid isalso known to react with NADH or related compounds (for example, NADPH)in the presence of formaldehyde dehydrogenase to yield formaldehyde, butthe process is impractical because NADH is very expensive. Formic acidcan also react with lithium aluminum hydride and sodium borohydride toform formaldehyde at low selectivity but again the process isimpractical on an industrial scale.

In particular, the present process includes a step in which formic acidis converted directly or indirectly via a non-biological reaction to atleast one of formaldehyde, acrylic acid, ethylene, propylene, syngas,and C5-C7 carbohydrates, without a separate process step in which formicacid is first converted to methanol. Presently, none of these chemicalsare synthesized from formic acid on an industrial scale. Formaldehyde ismade industrially from the oxidation of methanol. Acrylic acid is madefrom the oxidation of propylene. Ethylene and propylene are usually madevia cracking of petroleum, or from methanol via the methanol to olefinsprocess. Syngas is usually made via steam reforming of natural gas, butit can also be made from petroleum or coal. Most methane comes from anatural gas well, although years ago it was also made from coal. C5-C7carbohydrates are usually extracted from biomass.

In the present process, formic acid can be generated from conversion ofcarbon dioxide. Formic acid can also originate from other sources aslong as the process includes a step in which formic acid is converteddirectly or indirectly to at least one of formaldehyde, acrylic acid,methane, ethylene, propylene, syngas, and C5-C7 carbohydrates, without aseparate process step in which either (a) more than 10% of the formicacid is converted to methanol, or (b) NADH or an alkali or alkalineearth hydride reacts with the formic acid.

In the present process, carbon dioxide obtained from a natural source orfrom an artificial chemical source, which would otherwise be present innature or which would be discharged by the artificial chemical sourceinto the environment, is converted to formic acid. The formic acid isthen converted to a mixture comprising at least one of formaldehyde,acrylic acid, ethylene, propylene, syngas, and C5-C6 carbohydrates.

In the present process for the production of formaldehyde, formic acidreacts over a metal oxide catalyst to yield a product comprisingformaldehyde. Suitable metal oxides include CaO, SrO, BaO, MnO₂, V₂O₅,Ta₂O₅, MoO₃, WO₃, TiO₂, TeO₂, Sb₂O₃, CeO₂, Sm₂O₃, Bi₂MoO₆, Ce₂(WO₄)₃,Bi₁₂TiO₂₀, PbTa₂O₆, Pb(VO₃)₂ and PbTiO₃ and/or other oxides containingat least one of Ca, Sr, Ba, Mn, V, Ta, Mo, W, Ti, Te, Sn, Sb, Ge, Be,Sm, and Pb.

In the present process for the production of carbohydrates, formic acidis converted to formaldehyde, and the formaldehyde then reacts viaeither the formose reaction or an aldol condensation to yieldcarbohydrates.

In the present process for the production of organic acids, formic acidreacts with an alkene or alkyne to yield an organic acid with at least 3carbon atoms. The present process forms acrylic acid by reacting formicacid with acetylene in the presence of a catalyst comprising at leastone of Cu, Ni, Fe, Co, Mn, Cr, Ag, Pd, Ru, Rh, Mo Au, Pt, Ir, Os, Re,and W. The present process employs homogeneous catalysts comprising oneor more of Cu, Ni, Fe, Co, Mn, Cr, Ag, Pd, Ru, Rh, Mo Au, Pt, Ir, Os,Re, and W, in which the catalyst is active for the reaction betweenformic acid and acetylene.

Without further elaboration, it is believed that persons familiar withthe technology involved here, using the preceding description, canemploy the present process to the fullest extent. The following examplesare illustrative only, and not meant to be an exhaustive list of allpossible embodiments, applications or modifications of the presentprocess.

Example 1 Conversion of Carbon Dioxide to Formic Acid

Example 1 illustrates the conversion of carbon dioxide to formic acid,using a modification of the methods in applicant's co-owned U.S. patentapplication Ser. No. 12/830,338. By way of background, electrolysis ofCO₂ to formic acid had been well known in the literature, but prior tothe '338 application those processes exhibited poor energy efficiency.The process described in the '338 application was the first todemonstrate high energy efficiency, but the rate was insufficient.

The present example provides a method to produce formic acid at a highefficiency and an improved rate. To provide the environmental benefit ofeffecting a net reduction in the amount of carbon dioxide greenhouse gasin the atmosphere, it is preferred that the CO₂ starting material beobtained from sources in which the CO₂ would otherwise have beenreleased into the atmosphere, such as combustion, fermentation, or themanufacture of cement or steel. The CO₂ could also be obtained fromexisting sources, such as in natural gas or oil deposits (includingfields in which CO₂ injection has been used for enhanced oil recovery),in subterranean pockets or pore spaces rich in CO₂, or even in theatmosphere itself. It is also preferred that the energy required for theconversion of CO₂ to formic acid would originate from a carbon-neutralenergy source, such as wind, solar, hydroelectric, tidal, wave,geothermal and/or nuclear.

As illustrated in FIG. 4, the electrochemical cell employed in Example 1includes a three-necked flask 101, palladium wire 102, working electrode103 (comprising carbon paper with palladium catalyst), referenceelectrode 104 (silver wire), platinum wire 105, counter electrode 106(platinum mesh), glass tube 107 for sparging gas, glass frit 108, andelectrolyte 109.

More specifically, the experiments in Example 1 employed a 15 mL threenecked flask 101. Glass sparging tube 107 with glass frit 108 was usedto inject the gas. Silver wire 104 was used as reference electrode. Thecounter electrode 106 was made by attaching a 25×25 mm platinum mesh 105(size 52) (Alfa-Aesar, Ward Hill, Mass.) to a 5 inch platinum wire(99.9%, 0.004 inch diameter). The working electrode was formed using apalladium wire 102 attached to carbon fiber paper 103 (GDL 35 BC, IonPower, Inc., New Castle, Del.) with palladium black (Alfa-Aesar, WardHill, Mass.) painted on both sides.

Prior to carrying out the experiments, the glass parts and the counterelectrode were put in a 50/50 v/v sulfuric acid/water bath for at least12 hours, followed by rinsing with Millipore filtered water (MilliporeCorporation, Billerica, Mass., USA). Later, they were placed in an ovenat 120° C. to remove residual water.

During the experiment, a catalyst ink comprising a catalytically activeelement (palladium) was prepared as follows: First 0.01 grams ofpalladium black (99.9% metals basis, Alfa-Aesar, Ward Hill, Mass.) wasmixed with 600 μL of Millipore water, 600 μL of Millipore isopropanoland 2 drops of Nafion solution (5%, 1100EW, DuPont, Wilmington, Del.)The mixture was sonicated for 3 minutes. In the meantime, carbon paperwith dimensions of 1 cm×2.5 cm was cut and placed under a heat lamp.Later, palladium ink was painted on carbon paper with a painting brushunder the heat lamp. After drying under a heat lamp for 30 min, theprocedure was repeated again to paint the palladium catalyst on theother side of the carbon paper. The painting process was repeated untilsubstantially all of the ink was transferred onto the carbon paper. Thecarbon paper was then dried in the air overnight. This yielded acatalyst with physical surface area of 4 mg/cm².

Electrolyte 109 was prepared by mixing 5 mL of Millipore water and 5 mLof EMIM-BF4 (≧97%, Sigma Aldrich, St. Louis, Mo.) to obtain 50% volumeratio ionic liquid solution. The mixture was then poured into the threeneck flask 101. Next, ultra-high-purity (UHP) argon was fed through thesparging tube 107 and glass frit 108 for 30 minutes. Before carbondioxide conversion, the carbon dioxide was bubbling through the spargingtube 107 for at least 30 min

Next, the working electrode, counter electrode and reference electrodewere all connected to an SI 1287 Solartron electrical interface(Solartron Analytical, Schaumburg, Ill., USA). Then, achronoamperametric measurement was performed by stepping from open cellpotential to −1.5V vs. Ag/AgCl.

The reaction was run for two days, and 750 μL samples were periodicallytaken out of the mixture for analysis by GC.

The GC analysis procedure was carried out as follows. The 750 μL samplewas placed in a GC injection vial. 110 μL methanol and 75 μL 0.1Msulfuric acid were injected into the vial to functionalize the formicacid to methyl formate. After 90 minutes, the head space over the samplewas injected into an Agilent 6980N GC and the methyl formate peak areawas calculated. A calibration curve was used to compute how much formicacid was formed.

FIG. 5 shows how the GC trace of the functionalized formic acid grewwith time. Clearly, formic acid was being produced in the reactor. Thegas chromatogram (GC) trace shown in FIG. 5 was a taken during CO₂conversion to formic acid following the procedures in Example 1 herein.The samples were taken after 1370 minutes (peak 120), 1850 minutes (peak121), and 2900 minutes (peak 122). The peak near 1.53 minutes isassociated with formic acid. The peak near 1.50 minutes is associatedwith the methanol used to functionalize the formic acid.

Example 2 Hydrogenation of Formic Acid to Formaldehyde

The objective of Example 2 is to demonstrate that formic acid can behydrogenated to formaldehyde using catalysts such as CeO₂ and TeO₂. Byway of background, formaldehyde is currently made industrially viaoxidative dehydrogenation of methanol. In 1912, Sabatier and Maihe(Compt. Rend., 152: pages 1212-1215 (1912); “the Sabatier paper”)reported that formic acid reacts on one of two pathways on most metalsand metal oxides, namely: a dehydrogenation pathway:HCOOH→H₂+CO₂  (1)or a dehydration pathway:HCOOH→H₂+CO  (2)Sabatier's paper further indicates that formaldehyde (H₂CO) can form atlow rates during formic acid decomposition on a thorium oxide (ThO₂)catalyst, via the reaction:2HCOOH→H₂O+H₂CO+CO₂  (3)

The rates of these reactions are too small to be practical, however.Barteau and coworkers also found transient formaldehyde formation viareaction 3 during TPD of formates in UHV (H. Idriss, V. S. Lusvardi, andM. A. Barteau, Surface Science 348(1-2), pages 39-48 (1996); K. S. Kimand M. A. Barteau, Langmuir 6(9): pages 1485-1488 (1990). Górski et al.(Journal of Thermal Analysis, Vol. 32, pages 1345-1354 (1987)) foundtraces of transient formaldehyde formation in a reaction between metalformates and NaBH₄. Formate ions can also react with NADH or NADPH onformaldehyde dehydrogenase (FDH) to form formaldehyde. Still, except forprocesses using NADH or NADPH, there is no apparent evidence from thepublished journal or patent literature that formic acid could beconverted to formaldehyde at steady state with selectivities above 5percent, where the selectivity is calculated asSelectivity=(moles of formaldehyde formed)/(moles of formic acid used).This is insufficient for industrial practice. Processes involving NADHor NADPH or microbes are also too expensive to be used in mostindustrial production.

The present process provides a route to the conversion of formic acid toformaldehyde at high selectivity via the reactionHCOOH+H₂→H₂O+H₂CO  (4)The reviews of formic acid decomposition by Trillo et al. (CatalysisReviews 7(1), pages 51-86, (1972)) and by Mars (Advances in Catalysis14, pages 35-113 (1963)) contain no mention of reaction (4) above.Similarly, the review of ceria catalysis by Trovarelli (CatalysisReviews: Science and Engineering 38:4, pages 439-520 (1996)) and byIvanova (Kinetics and Catalysis, Vol. 50, No. 6, pages 797-815 (2009))contain no mention of reaction (4) above.

The experimental apparatus for the conversion of formic acid toformaldehyde in Example 2 is shown in FIG. 6. The experimental apparatusincludes GC injector coupled with an Agilent 7683B autosampler 151,intermediate polarity (IP) deactivated capillary guard column 152(length=30 cm, inside diameter=250 μm), 1/16 inch nut 153, reducing 1/16inch to ⅛ inch reducing union 154, ⅛ inch nut 155, glass tube 156 (7.6cm length, 3 mm OD, 1.75 mm ID), quartz wool 157, catalyst 158, ZebronZB-WAX-Plus capillary GC column 159 (30 m×250 μm×0.25 μm), Agilent 5973NMass Selective Detector (MSD) 160, and Agilent 6890N GC oven 161.

In the experiments of Example 2, catalyst 158 were packed into glasstube 156, and quartz wool plugs 157 were inserted into both ends of theglass tube to hold the catalyst. The entrance of the catalyst packedglass tube 156 was connected to IP deactivated guard column 152 with1/16 inch nut 153, reducing union 154, and ⅛ inch nut 155. IPdeactivated guard column was connected to a GC injector that coupledwith an Agilent 7683 autosampler 151, while the exit of the catalystpacked glass tube 156 was connected to a Zebron (Phenomenex, Torrance,Calif.) ZB-WAX-Plus capillary GC separation column 159 (30 m×250 μm×0.25μm). The other side of the GC separation column 159 was inserted into5973 N MSD 160. The entire apparatus was placed into an Agilent 6890 NGC oven 161.

Prior to the experiments, the catalysts, such as cerium (IV) oxide(99.9% metal basis from Alfa Aesar, Ward Hill, Mass.) and tellurium (IV)oxide (99.9% metal basis from Alfa Aesar, Ward Hill, Mass.) wereconditioned in a box oven (Lindberg/Blue M from Thermo ElectronCorporation) at 250° C. for 4 hours. Cerium oxide pieces (3-6 mm) weregranulated to 20-100 mesh particles before packing.

The borosilicate glass tube (trade designation Pyrex, Corning Inc.,Corning, N.Y.) was cleaned with acetone (certified ACS from FisherScientific), and then rinsed with Millipore filtered water (MilliporeCorporation, Billerica, Mass., USA) and dried at 100° C. before catalystpacking. The catalyst packed bed was prepared by pouring the catalysts(0.2 to 0.5 gram) into a glass tube with shaking or tapping. The tubewas first positioned vertically against the workbench, the lower end ofthe tube was filled with quartz wool (serving as a frit to hold catalystparticles) and the upper end was attached to a funnel into which thesolid catalysts were fed. The shaking or tapping reduced voids in thetube and facilitated tight packing. Before the performance test thepacked bed column was purged with hydrogen (1.5 ml/min) at 100° C. for 2to 4 hours.

Experiments were performed on an Agilent Model 6890N gas chromatographequipped with a Model 5973N quadrupole mass selective detector (MSD) andModel 7683 autosampling unit. 0.2 μL of formic acid (Fluka, ˜98% fromSigma Aldrich, St. Louis, Mo.) was injected into the GC with the 7683autosampler; the injector was maintained at 200° C. with a split ratioof 100:1. The vaporized formic acid was introduced to the catalyst bedwith hydrogen, and the products from the catalyst bed were separatedusing a Zebron (Phenomenex, Torrance, Calif.) ZB-WAX-Plus column (100%polyethylene glycol), 30 m long with a 250 μm I.D. and 0.25 μm filmthickness. The carrier gas was hydrogen, which was set at a constantflow rate of 1.1 mL/min with a head pressure of 2.9 psi at 100° C. Thetransfer line was set at 200° C. The column oven temperature was set at100° C. or 150° C. isothermal for the testing of the CeO₂ packed bed.Mass selective detector detection was performed at 230° C. with eitherfull scan (15-150 amu) for identification or with selected ionmonitoring (SIM) mode for quantitative analysis. The qualifying ions forSIM mode were m/z 30 for formaldehyde (m/z 30 from formic acid is veryweak). Chromatographic data were collected and evaluated using MSDProductivity Chemstation Software.

FIG. 7 shows the abundance of the formaldehyde GC trace at differenttemperatures from the CeO₂ catalyst bed. Significant formaldehydeformation started to be observed at bed temperatures of 40° C. The rateof formaldehyde formation increased as the temperature was raised to 60°and 80° C., then there was a slow decay at higher temperatures. Theoptimal temperature was between 60° C. and 100° C. Very littleformaldehyde was detected at temperatures above 20° C. These resultsdemonstrate that formic acid can be hydrogenated to formaldehyde withhigh selectivity without first converting the formic acid to methanol.Further, the process performs well at temperatures much lower than the500-600° C. used to produce methanol commercially.

Similar tests were performed with TeO₂ and significant formaldehydeproduction was also found, as summarized in Table 1 below.

TABLE 1 Conversion and selectivity of the catalysts for formic acidhydrogenation to formaldehyde Optimized Approximate Catalyst TemperatureConversion Selectivity CeO₂ 80° C. 64% ~80% TeO₂ 80° C. 34% ~85%

One can speculate how this reaction occurs. Previous workers have foundthat an adsorbed formyl intermediate (H—C═O) forms during formic aciddehydration (namely, reaction (2) above) on most metal oxides. It isproposed here that the formyl species is being hydrogenated to yieldformaldehyde. The formyl intermediate can form on the oxides of Mg, Ca,Sr, Ba, Ti, Y, Lu, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Co, Ni, Cu, Zn,Al, Ga, In, Tl, Si, Ge, Sn, Sb, Bi, Se, Te, Pb, La, Ce, Pr, Th, Nd, Pm,U, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Therefore it is believed thatcatalysts comprising the oxides of Mg, Ca, Sr, Ba, Ti, Y, Lu, Ti, Zr,Hf, V, Nb, Ta, Cr, Mo, W, Fe, Co, Ni, Cu, Zn, Al, Ga, In, Tl, Si, Ge,Sn, Sb, Bi, Se, Te, Pb, La, Ce, Pr, Th, Nd, Pm, U, Sm, Eu, Gd, Tb, Dy,Ho, Er, Tm, and/or Yb are active for formic acid hydrogenation toformaldehyde. Generally the formyl species is stable up to about 350° C.Therefore, it is expected that the reaction temperature should be below350° C. This compares to 500-600° C. in the conventional synthesis offormaldehyde. It is also believed that the temperature should be above8° C., as formic acid freezes at 8.4° C.

Example 3 Conversion of Formic Acid to C5-C6 Carbohydrates

The objective of Example 3 is to demonstrate that carbohydrates can beformed from formic acid. By way of background, the conversion offormaldehyde to mixed carbohydrates via the formose reaction is known.For example, the reactionnH₂CO+H₂O→HO(CH₂O)_(n)H  (5)is disclosed in U.S. Pat. Nos. 2,224,910, 2,760,983, and 5,703,049, andin Iqbal and Novalin, Current Organic Chemistry 16, page 769 (2012; “theIqbal paper”). See also Shigemasa et al., Bul. Chem. Soc. Japan 48, page2099 (1975). It is believed that there is no previous report ofcarbohydrate synthesis starting with formic acid. The present processprovides such a procedure, namely:

-   -   (1) Converting the formic acid to formaldehyde according to the        procedures set forth in Example 2 herein;    -   (2) Reacting the formaldehyde via the methods described in U.S.        Pat. Nos. 2,224,910 and 2,760,983 to form a mixture of C3 to C7        carbohydrates.

In the remainder of this section, an improved procedure for step (2)above will be provided, which produces mainly C5 and C6 sugars.

In Example 3, 40 mL of deionized water was mixed with 4.5 mL of 37%formaldehyde. This solution was heated to 60° C. for an hour. Aftertemperature stabilization, 425 mg of Ca(OH)₂ was added to the solution.The reaction was run under N₂ gas flow (200 sccm), with magneticstirring for homogeneity. 1 mL aliquots were taken at 30 minutes and 45minutes, and then the heat was turned off (but the N₂ flow and stirringremained active for another 1.5 days). One final aliquot was taken after1.5 days. Table 2 below shows the products formed after 1.5 days. Theliquid chromatography (LC) analysis here identified three major species,C6 sugars, C5 sugars, and calcium salts of C6 sugars. Tandem massspectrometry (MS/MS) of the C6 fragments showed that the C6 sugarsconsisted of either glucose or galactose, or a mixture of the two.

TABLE 2 Products formed in Example 3 C5 sugars 5% C6 sugars 85% Calciumsalt of C6 10%

These results demonstrate that formic acid can be converted to a mixtureof C5 and C6 sugars without first converting the formic acid tomethanol.

Example 4 Conversion of Formic Acid to Olefins (Ethylene, Propylene,Butene)

The objective of Example 4 was to demonstrate the conversion of formicacid to olefins such as ethylene, propylene and butene. Example 4illustrates the manufacturing of olefin gas from formose sugar in thepresence of the zeolite catalyst SAPO-34. By way of background, U.S.Pat. Nos. 4,503,278, 4,549,031, 6,437,208, 6,441,262, 6,964,758,7,678,950, 7,880,049, 8,148,553, and 8,231,857 disclose thatcarbohydrates can be converted to hydrocarbons by a number of differentprocesses. In each case, the processes start with pure sugar solutionswith no basic impurities such as calcium. A further objective of Example4 is to demonstrate that olefins can be produced without removing thecalcium.

The experiments of Example 4 were carried out under static conditions.179 mL of formose sugar solution/calcium solution was synthesized asdescribed in Example 3 without further purification. CO₂ was bubbledthrough the mixture to lower the pH to 6.2, and the precipitate wasremoved by filtration. The formose sugar solution and 18 grams ofSAPO-34 (Sigma-Aldrich, Milwaukee, Wis.) were charged into an Alloy C276pressure reaction apparatus with a capacity of 600 mL (Parr InstrumentCompany, Moline, Ill.) designed for a maximum working pressure of 3000psi at 350° C. The reactor had facilities for gas inlet, gas and liquidoutlet, cooling water inlet and outlet, temperature controlled externalheating and variable agitation speed. A Parr 4843 controller (ParrInstrument Company, Moline, Ill.) was used to control the heating andstirring speed and to monitor the reactor's real temperature andpressure. After purging the reactor with nitrogen gas (S.J. Smith Co.,Urbana, Ill.) for about 4 minutes, the gas inlet and outlet were thenclosed. The reactor was then heated to 300° C. within 40-50 minutes,whereby system pressure increased to 1300 psi. The reaction proceeded at300° C. for 12-15 hours, and then the reaction system was cooled to roomtemperature.

A gas phase sample was collected with a Tedlar bag and analyzed with anAgilent Model 6890N gas chromatograph equipped with a Model 5973Nquadrupole mass selective detector (MSD) and Model 7683 autosamplingunit. A 5 μL gas sample was injected into the GC with 7683 autosampler,and the injector was maintained at 250° C. with a split ratio of 10:1.Compounds were separated using a GS-Carbon PLOT column (AgilentTechnologies, Santa Clara, Calif.), 27 m length with a 320 μm I.D. and3.0 μm film thickness. The carrier gas was helium and was set at aconstant flow rate of 2.5 mL/min with a head pressure of 5.91 psi at 40°C. The transfer line was set at 200° C. The column oven temperature wasprogrammed from 40° C. to 200° C. with ramping rate at 20° C./min. Massselective detector detection was performed at 230° C. with full scan(15-300 amu) for identification. As shown in FIG. 8, olefin gases suchas ethylene, propene and butene were detected in the gas phase, andsmall amounts of methane and ethane were also detected.

Example 5 Conversion of Formic Acid to Propylene

The objective of Example 5 is to demonstrate that formic acid can beconverted to propene. By way of background, U.S. Pat. Nos. 4,503,278,4,549,031, 6,437,208, 6,441,262, 6,964,758, 7,678,950, 7,880,049,8,148,553, and 8,231,857 disclose that carbohydrates can be converted tofuels or olefins by a number of different processes but generally amixture of a large number of hydrocarbons is produced. Here, a processis described that produces mainly propylene with smaller amounts ofbutene and ethylene. An important aspect of the processes is to not usenaturally occurring carbohydrates as a starting material. Instead,carbohydrates produced by the Formose Reaction can be used as a startingmaterial, and the carbohydrates then converted to hydrocarbons.

The procedure used in Example 8 was identical to that in Example 5except that ZSM-5 (Sigma-Aldrich, Milwaukee, Wis.) was substituted forthe SAPO-34, and the reaction was run for only 4 hours.

FIG. 9 shows a GC trace taken from the gas phase at the end of theprocess. The magnitude of propylene peak 410 indicated that propylenewas the major reaction product, with the lesser magnitudes of ethylenepeak 411 and butene peak 412 indicating that ethylene and butene werepresent in much smaller quantities. Dimethyl ether peak 413, water peak414. CO₂ peak 415, and air peak 416 indicate the presence of thoseconstituents, but they are not reaction products.

Example 8 shows that ZSM-5 can be used to convert formic acid topropylene with reasonably high selectivity.

It is also known that propylene can be converted to hydrocarbon fuelsusing a process called alkylation. In the present process for theformation of hydrocarbon fuels, formose sugars are converted tohydrocarbon fuels. In particular, the present process employs zeolitecatalysts such as ZSM-5 in the conversion of formic acid and/or formosesugars to hydrocarbon fuels.

U.S. Pat. Nos. 4,503,278, 4,549,031, 6,437,208, 6,441,262, 6,964,758,7,678,950, 7,880,049, 8,148,553, and 8,231,857 disclose many othercatalysts that can be used to convert oxygenates to hydrocarbons. Thepresent process encompasses the use of catalysts disclosed in theseprior patents in the conversion of formic acid to hydrocarbons.

Example 6 Conversion of Formic Acid to Acrylic Acid

The objective of Example 6 is to demonstrate that formic acid can beconverted to acrylic acid (H₂C═CHCOOH). By way of background, acrylicacid is currently made by oxidation of propylene. U.S. Pat. Nos.2,806,040, 2,925,436 and 2,987,884 disclose that acrylic acid can alsobe made via the reaction:CO+H₂O+HC≡CH→H₂C═CHCOOH  (6)This reaction is not commercially practical, however, because highpressures and temperatures are required.

Reaction (5) above provides a route to the conversion of formic acid toacrylic acid. The process is as follows:

-   -   (1) Formic acid is reacted on a strongly acidic cation exchange        resin, such as one available under the trade designation Dowex        50WX8 hydrogen form (Sigma Aldrich, St. Louis, Mo.) to yield CO        and H₂O via reaction (2) as was demonstrated in Example 2 above.    -   (2) The CO is purified by removing water.    -   (3) The CO and water are reacted with acetylene at 100 atm and        200° C. on a nickel bromide catalyst according to the teachings        of U.S. Pat. Nos. 2,806,040, 2,925,436 and U.S. Pat. No.        2,987,884 to yield acrylic acid.

This is not the only way to create acrylic acid from formic acid withoutgoing through methanol as an intermediate. In particular, Example 6illustrates the manufacturing of acrylic acid or its derivatives fromformic acid and acetylene via the reaction:HCOOH+HC≡CH→H₂C═CHCOOH  (7)in the presence of palladium acetate and phosphine ligand under mildconditions. Tang, et al. (Journal of Molecular Catalysis A: Chemical314, pages 15-20 (2009)) had previously demonstrated thattrifluoromethane sulfonic acid-promoted palladium acetate can catalyzereaction (6) above under mild conditions. The example below demonstratesthat reaction (7) above can also occur under similar conditions.

The experimental apparatus for Example 6 is shown in FIG. 10. Catalystpacked bed 306 was constructed from a glass tube packed with ionexchange resin, available under the trade designation Dowex 50WX8, withquartz wool plugs at both ends. A K-type thermocouple 307 was heldsnugly against the outer glass wall and a flexible electric heating tape309 (Cole Parmer, Vernon Hills, Ill.) was coiled around the glass tubeto create a heated region. The temperature of catalyst packed bed 306was measured with thermocouple thermometer 308 (Barnant 100, BarnantCompany, Barrington, Ill., USA). A Variac W10MT3 autotransformer 310(Variac, Cambridge, Mass.) was used to apply adjustable voltage to theheating tape 309. The upstream end of catalyst packed bed 306 wasconnected to a bubbler 302 that contained formic acid with a 1/16 inchnut 303, a 1/16 inch to ⅛ inch reducing union 304, a ⅛ inch nut 305, and⅛ inch Tygon tubing. The downstream end of catalyst packed bed 306 wasattached to a bubbler 311, which contained concentrated H₂SO₄. Theresultant gas was introduced into the reaction mixture by a stainlesssteel needle 313. A water condenser 316, thermometer 319, CO gas line313 and acetylene gas line 314 were connected to a 3-neck flask immersedin a 55° C. water bath 320.

Prior to carrying out the reaction, the Dowex 50WX8 catalyst was airdried overnight and the Pyrex glass tube was cleaned with acetone(certified ACS from Fischer Scientific), then rinsed with Milliporefiltered water (Millipore Corporation, Billerica, Mass., USA), and driedat 100° C. before catalyst packing. The catalyst packed bed was preparedby pouring 1.3435 grams of catalyst into a glass tube with shaking ortapping. The tube was first positioned vertically against the workbench,the lower end of the tube was filled with quartz wool (serving as a fritto hold catalyst particles), and the upper end was attached to a funnelinto which the solid catalysts were fed. The shaking or tapping reducedvoids in the tube and facilitated tight packing.

The experiments were carried out under dynamic conditions. A mixture of50 mL of acetone (Fisher Scientific), 10 mL of deionized (DI) water,0.01150 grams of palladium acetate (Sigma-Aldrich, Milwaukee, Wis.),0.3989 grams of diphenyl-2-pyridylphosphine (Sigma-Aldrich, Milwaukee,Wis.), 0.3742 g inhibitor hydroquinone (Sigma-Aldrich, Milwaukee, Wis.)and 0.29 ml trifluoromethane sulfonic acid (Sigma-Aldrich, Milwaukee,Wis.) were charged into a 100 mL 3-neck flask (Chemglass, Vineland,N.J.) The reaction temperature was controlled with a water bath and setat 50-55° C. Formic acid (Fluka, ˜98% from Sigma Aldrich) vapor from thefirst bubbler 302 was introduced into the catalyst packed bed bynitrogen gas line 301. The temperature of the catalyst packed bed couldbe adjusted by varying the voltage applied to the flexible electricheating tape and was maintained at 145-150° C. The products produced inthe bed were passed through a bubbler of concentrated sulfuric acid 311.The gas exiting the bubbler was combined with acetylene from gas tank312, which were then both bubbled through the reaction mixture. Thereaction proceeded at 50-55° C. for several hours, and samples weretaken at different intervals for gas chromatography mass spectrometry(GC/MS) analysis.

A liquid phase sample of the reaction product was analyzed with anAgilent GC/MS instrument which consisted of a 6890N gas chromatograph,5973N quadrupole mass selective detector (MSD) and 7683 autosampler. Analiquot of 0.2 μL sample was injected into the GC with 7683 autosampler,and the injector was maintained at 250° C. with a split ratio of 100:1.Compounds were separated using a Phenomenex Zebron ZB-WAX-Plus column(100% polyethylene glycol) that was 30 m length with a 250 μm I.D. and0.25 μm film thickness (Phenomenex Torrance, Calif., USA). The carriergas was helium and was set at a constant flow rate of 1.0 mL/min with ahead pressure of 7.1 psi at 40° C. The transfer line was set at 280° C.The column oven temperature was programmed from 40° C. to 200° C. with aramping rate of 20° C./min. Mass selective detection was performed at230° C. with full scan (15-300 amu) for identification.

After 80 minutes reaction time, acrylic acid was identified in theliquid phase. FIG. 11 illustrates the growth of the acrylic acid peakarea, and shows that significant quantities of acrylic acid can beformed. Example 6 thus illustrates the manufacturability of acrylic acidor its derivatives from acetylene and formic acid under mild conditions.

Additional experiments have been performed to identify the effects ofvarying reaction conditions. It has been found that the reaction occursas long as the packed bed temperature is at least 100° C. and proceedswith even higher yields when the packed bed temperature is at least 140°C.

The data here were taken using a palladium acetate catalyst. However,Tang et al. (Catalysis Letters 129, pages 189-193 (2009)) demonstratedthat reaction (6) is more selective on a mixed copper bromide, nickelacetate catalyst, while Kiss (Chem. Rev. 101 (11), pages 3435-3456(2001), Jayasree, et al. (Catalysis Letters 58, pages 213-216 (1999)),Drent, et al. (Journal Of Organometallic Chemistry 475, pages 57-63(1994)) and Brennführe et al. (Chem. Cat. Chem. 1, pages 28-41 (2009))propose that other palladium based catalysts are preferred for reaction(6). It could be expected that these catalysts would also be useful forreaction (7) above.

Kiss (Chem. Rev. 101 (11), pages 3435-3456 (2001)) and Brennführe et al.(Chem Cat Chem. 1, pages 28-41 (2009)) teach that one can make a largenumber of organic acids by replacing the acetylene in reaction (6) withan alkene or a different alkyne to yield an organic acid with 3 or morecarbons. It is anticipated that formic acid, rather than CO and water,could be successfully employed as a reactant using similar chemistry.For example, the reaction with ethylene is expected to yield propionicacid. The reaction with methylacetylene (propyne) is expected to yieldmethyl acrylic acid (MAA).

Example 7 Conversion of Formic Acid to Hydrogen

Example 7 illustrates the conversion of formic acid to hydrogen and CO₂via reaction (1) above, consistent with the teachings in the SabatierPaper. The experimental apparatus for Example 7 is shown in FIG. 12.Catalyst packed bed 186 was constructed from a glass tube. A K-typethermocouple 187 was held snugly against the outer glass wall with blacktape, and Chromel wire heater 189 (0.31 mm diameter) was coiled aroundthe glass tube to create a heated region. The temperature of catalystpacked bed 186 was measured with a thermocouple thermometer 188 (Barnant100, Barnant Company, Barrington, Ill., USA). A dual output DC powersupply 190 (Agilent, E3647A) was used to heat the Chromel wire heater189. One side of the catalyst packed bed 186 was connected to a bubbler182 that contained formic acid with a 1/16 inch nut 183, a 1/16 inch to⅛ inch reducing union 184, a ⅛ inch nut 185 and ⅛ inch Tygon tubing. Theother side of catalyst packed bed 186 was connected to a 1 ml 10-portvalve sampling loop 194. The upstream and downstream connections of amolecular sieve 5A packed bed column 195 (length=6 feet; insidediameter=8 inches) were connected with a 10-port valve 191 and a thermalconductivity detector 196, respectively. 10-port valve 191 and thepacked column 195 were placed into an SRI 8610C GC 197. Nitrogen from agas tank 181 was bubbled through a bubbler 182 to carry the formic acidvapor through the catalyst packed bed 186. The flow rate through thecolumn was controlled with an 8610C GC built-in electronic pressurecontroller module.

Prior to the experiments in Example 7, the palladium catalyst (5% onalumina pellets; available from Alfa Aesar, Ward Hill, Mass.), wasconditioned in a box oven (Lindberg/Blue M from Thermo ElectronCorporation, now Thermo Fisher Scientific, Waltham, Mass., USA) at 300°C. for 4 hours and granulated to 20-100 mesh particles before packing.

A Pyrex glass tube was cleaned with acetone (certified ACS grade fromFisher Scientific, Pittsburgh, Pa.), and then rinsed with Milliporefiltered water (Millipore Corporation, Billerica, Mass., USA) and driedat 100° C. before catalyst packing. The catalyst packed bed was preparedby pouring 0.15 grams of catalyst into a glass tube with shaking ortapping. The tube was first positioned vertically against the workbench,the lower end of the tube was filled with quartz wool (serving as a fritto hold catalyst particles) and the upper end was attached to a funnelinto which the solid catalysts are fed. The shaking or tapping reducedvoids in the tube and facilitated tight packing. Before the performancetest the packed bed column was purged with nitrogen saturated withformic acid vapor at room temperature for 1 to 2 hours.

Experiments were performed on an SRI 8610C gas chromatograph equippedwith a thermal conductivity detector (TCD). Formic acid (Fluka, ˜98%from Sigma Aldrich, St. Louis, Mo.) vapor was introduced into thecatalyst packed bed by nitrogen gas, which also served as carrier gasfor column separation and reference gas for the TCD. The temperature ofthe catalyst packed bed could be adjusted by varying the voltage appliedto the Chromel wire heater. The products from the catalyst bed wereseparated using a molecular sieve 5A packed column (length=6 feet, OD=⅛inch, from Restek, Bellefonte, Pa.) and detected with TCD. The carriergas was nitrogen and was set at 10 psi. The column oven temperature wasset at 100° C. isothermal for the separation. The temperature of the TCDwas maintained at 116° C. Chromatographic data were collected andevaluated using PeakSimple Software (version 4.07, available as a freedownload from various sources). Error! Reference source not found. belowlists the hydrogen peak area from the Pd catalyst bed at varioustemperatures. The data show that formic acid is converted to CO₂ andhydrogen when the temperature of the catalyst packed bed is between 40and 63° C.

TABLE 3 Hydrogen peak area from Pd catalyst packed bed at differenttemperatures Catalyst bed Hydrogen peak temperature (° C.) area from TCD25.2 0 40 145 63.5 121

The data here were taken on a palladium catalyst, but Ojeda and Iglesia(Angew. Chem. 121, pages 4894-4897 (2009)) claim that nano-gold ispreferred. Indeed reaction (1) above has been previously observed on Cr,Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, Au, Pb, Bi, and Sb

Example 8 Conversion of Formic Acid to Carbon Monoxide

Example 8 demonstrates that formic acid can be converted to CO and watervia reaction (2), consistent with the Sabatier Paper. The procedurefollows closely the work of Gates and Schwab (J. Catalysis 15(4), pages430-434 (1969)).

The apparatus employed in Example 8 is shown in FIG. 12. A Pyrex glasstube (7 inch length, 6 mm OD, 4 mm ID) was cleaned with acetone(certified ACS from Fisher Scientific), and then rinsed with Milliporefiltered water (Millipore Corporation, Billerica, Mass., USA) and driedat 100° C. before catalyst packing. The catalyst packed bed was preparedby pouring 1.3 gram of catalyst (trade designation “Dowex 50WX8 hydrogenform”, 50-100 mesh (Sigma-Aldrich)) into a glass tube with shaking ortapping. The tube was first positioned vertically against the workbench,the lower end of the tube was filled with quartz wool (serving as a fritto hold catalyst particles) and the upper end was attached with a funnelinto which the solid catalysts were fed. The shaking or tapping reducedvoids in the tube and facilitated tight packing. Before the performancetest the packed bed column was conditioned at 120-150° C. under heliumfor 3 hours.

Experiments were performed on an SRI 8610C gas chromatograph equippedwith a thermal conductivity detector (TCD.) Formic acid (98-100%, SigmaAldrich, St. Louis, Mo.) vapor was introduced into the catalyst packedbed by helium gas which also served as the carrier gas for columnseparation and the reference gas for the TCD. The temperature of thecatalyst packed bed was adjustable by varying the voltage applied to theChromel wire heater. The products from the catalyst bed were separatedusing a molecular sieve 5A packed column (6 feet length, ⅛ inch OD, fromRestek) and detected with the TCD. The carrier gas was helium at 10 psi.The column oven temperature was set at 100° C. isothermal for theseparation. The temperature of the TCD was maintained at 116° C.Chromatographic data were collected and evaluated using PeakSimpleSoftware (version 4.07).

FIG. 13 shows the chromatogram of the product of formic acid through thecatalyst bed at different temperatures. Peak 201 denotes formic acidsaturated helium through catalyst packed bed with bed temperature at100° C. Peak 202 denotes formic acid saturated helium through catalystpacked bed with bed temperature at 130° C. Peak 203 denotes formic acidsaturated helium through catalyst packed bed with bed temperature at168° C. Peak 204 denotes a trace of pure carbon monoxide from a gasbottle It should be noted that no CO is detected at a bed temperature of100° C., but a CO peak is observed when the catalyst bed temperature isgreater than 130° C. This result shows clearly that formic acid can beconverted to CO via reaction (2) above.

Example 8 represents one example of a process to form carbon monoxide,but the reviews of Trillo, et al. (Catalysis Reviews 7(1), pages 51-86(1972)) and Mars (Advances in Catalysis 14, pages 35-113 (1963))indicate that formic acid decomposes to CO and water on most acidicmetal oxides. Mineral acids, such as sulfuric acid and nitric acid, havealso been reported to catalyze the reaction.

Example 9 Conversion of Formic Acid to Syngas

Example 9 demonstrates that formic acid can be converted to syngas. Theprocedure is as follows: The hydrogen produced in Example 7 is mixedwith the carbon monoxide produced in Example 8 in a volumetric ratio ofthree parts hydrogen to one part carbon monoxide to yield syngas.

Persons familiar with the technology involved here will recognize thatonce syngas is produced, one can make a wealth of compounds includingfuels and chemicals, such as methanol (see FIG. 1) or methane (using theSabatier methanation reaction). The present process encompasses theproduction of hydrocarbon fuels from formic acid.

While particular elements, embodiments and applications of the presentinvention have been shown and described, it will be understood that thepresent invention is not limited thereto, since modifications can bemade by those skilled in the art without departing from the scope of thepresent disclosure, particularly in light of the foregoing teachings.

What is claimed is:
 1. A catalytic process for the production offormaldehyde comprising hydrogenating an amount of formic acid to form aproduct comprising formaldehyde, wherein said formaldehyde is formedwithout hydrogenating more than 10% of said amount of formic acid tomethanol, wherein the process is catalyzed by a catalyst comprising atleast one of Ce (IV) oxide and Te (IV) oxide.
 2. The catalytic processof claim 1, further comprising initially converting an amount of carbondioxide obtained from a natural source or from an artificial chemicalsource to produce said amount of formic acid, thereby reducing saidamount of carbon dioxide present in nature or diverting said amount ofcarbon dioxide from being discharged into the environment by saidartificial chemical source.
 3. The catalytic process of claim 1, whereinreaction temperature is between 8° C. and 350° C.
 4. The catalyticprocess of claim 3, wherein said reaction temperature is between 40° C.and 200° C.
 5. The catalytic process of claim 4, wherein said reactiontemperature is between 60° C. and 100° C.